Updated at 10:46 p.m. ET: TEL AVIV -- The head of the militant wing of the Palestinian Hamas movement and seven others were killed as Israel launched a series of airstrikes in Gaza Wednesday, officials said.

Hamas spokesman Fauazy Brehom told NBC News that Ahmed Jabari was killed in the attack by Israeli forces. Jabari was the most senior commander of Hamas' military wing, the Ezzidine Al-Qassam Brigades.

A statement from the Al-Qassam Brigades said that Israel had “opened the gates of hell.”

President Barack Obama spoke with Israeli Prime Minister Benjamin Netanyahu Wednesday, urging him to avoid civilian casualties. The president reiterated the United States' support for Israel's right to self-defense following rocket attacks launched from Gaza.

Obama also spoke Wednesday with Egyptian President Mohammed Morsi because of the country's central role in preserving regional security. Obama condemned the rocket fire from Gaza into Israel and reiterated Israel's right to self-defense. The two leaders agreed on the importance of working to deescalate the situation quickly and they agreed to stay in touch in coming days.

"If I were a senior Hamas activist - I would look for a place to hide," IDF spokesman Brgi. Gen. Yoav (Poly) Moredechai said in a statement published online.

Moredechai said the possibility of a ground invasion would not be ruled out, and emphasized that all options remain on the table. "Infantry brigades have been shifted in preparation for the operation," his statement read. "All options that allow us to cause seriously damage to Hamas and the other terrorist organizations are on the table."

A statement from the Israeli embassy blamed Hamas for launching 150 rockets at Israel's south over the past week.

Darren Whiteside / Reuters

Smoke rises after Israeli air strikes in the northern Gaza Strip on Nov. 14. Israel launched a major offensive against Palestinian militants in Gaza on Wednesday, killing the military commander of Hamas in an air strike and threatening an invasion of the enclave that the Islamist group vowed would "open the gates of hell."

"Israel has the right and duty to defend itself from terrorist attacks designed to kill thousands of its citizens," Israeli Ambassador to the United States Michael Oren said. "We are sending an unequivocal message that our citizens will not be hostage to terrorist missile fire and cross-border attacks. The scope of the IDF's defensive operation depends on Hamas and whether it takes the decision to cease firing missiles on our neighborhoods and homes."

Jabari is the most senior Hamas official to have died due to Israeli military action since the killing of Saeed Seyam four years ago.

Sources at the Kamal Adwan and Al-Shifa hospitals said a total of eight people had been killed and 80 injured.

A statement on the IDF website said that Chief of Staff Lt. Gen. Benny Gantz had “approved an expansive strike against terrorist organizations in Gaza.”

Ali Ali / EPA

Emergency services extinguish the burned out destroyed car of Qassam top leader Ahmed Jabari after an Israeli air strike in Gaza City on Wednesday, Nov. 14, 2012.

“As a part of the program, a short while ago, the Israeli Air Force (IAF) struck Ahmed al-Jabari and other senior officers of Hamas' Military Wing, who were involved in planning and implementing dozens of attacks, including the kidnapping of SFC [Israeli soldier] Gilad Shalit,” it said.

The airstrike took place in central Gaza, according to the statement, which was headlined "Chief of Hamas' Military Wing Ahmed al-Jabari assassinated." The headline was later changed to "Senior Hamas operative targeted," and the statement dropped the reference to Shalit.

The statement quoted IDF spokesman Mordechai as saying military action began following the "intolerable situation in the south of the country, and seeks to harm terrorist organizations operating in the Gaza Strip."

'Forward base for Iran'The IDF later announced it had begun "Operation Pillar of Defense." Israel confirmed there had been several airstrikes.

Hamas Office via Reuters, file

Ahmed Al-Jabari, top commander of Hamas armed wing Al-Qassam brigades, poses for a picture after a prisoner swap deal between Hamas and Israel, in Cairo, in this October 18, 2011 file photo.

In another update, the statement said the IDF had "targeted a significant number of long range rockets sites ... owned by Hamas. This deals a significant blow to the terror organizations' underground rocket launching capabilities and munitions warehouses that are owned by Hamas and other terror organizations."

"The Gaza strip, has turned it into a forward base for Iran, firing rockets and carrying out terrorist attacks against Israeli citizens. The IDF will continue to target terrorist sites that are used to carry out terror attacks against Israeli citizens," it said.

"The IDF will continue to target sites that are used for carrying out terror attacks against the citizens of Israel while improving their daily security," it added.

An IDF statement Monday saidmore than 120 rockets fired from Gaza had hit Israel since Saturday and that the Israeli air force had responded with airstrikes on a number of sites.

Jabari had survived numerous assassination attempts in the past and had served close to a decade in an Israeli jail, according to NBC's Ayman Mohyeldin.

He was widely considered the second most important figure within Hamas' overall structure after Khaled Mishaal, the head of the organization’s political bureau.

Uriel Sinai / Getty Images

Israeli children play games at a bomb shelter on Nov. 14 in Netivot, Israel. Israel Defense Forces launched aerial attacks on targets in Gaza that killed the top military commander of Hamas.

Jabari was instrumental in negotiations about the release of Shalit, Mohyeldin said. Jabari was rarely seen in public and even more seldom filmed but he was seen accompanying Shalit to the border crossing with Egypt ahead of his handover.

US reacts; Israeli ambassador leaves EgyptU.S. State Department spokesman Mark Toner said the United States "strongly" condemns the rocket fire from Gaza into southern Israel.

"There is no justification for the violence that Hamas and other terrorist organizations are employing against the people of Israel," Toner's statement read. "We call on those responsible to stop these cowardly acts immediately. We support Israel's right to defend itself, and we encourage Israel to continue to take every effort to avoid civilian casualties."

Egypt's foreign minister called Israel's airstrikes on Gaza a dangerous escalation at a critical time for the region, and called on the Israeli government to quickly halt the offensive.

Egypt's ruling Freedom and Justice Party condemned the killing of Jabari, and said Israel was using the military operation as a card in its own political game, ahead of elections in January. The party called on the international community and Arab states to act immediately to stop the massacre against the Palestinian people, adding that Israel's attacks were meant to create instability in the region.

Airport sources in Egypt confirmed to NBC News that the Israeli ambassador and other Israelis were leaving Cairo Wednesday night.

The U.N. chief also called on Israel and Palestinian Hamas militants to prevent an escalation of hostilities, urging both sides to ensure civilians will be protected, a U.N. spokesman said Wednesday.

"The Secretary-General calls for an immediate de-escalation of tensions," U.N. spokesman Martin Nesirky said, adding that it was a reiteration of Ban's already-stated position.

"Both sides should do everything to avoid further escalation and they must respect their obligations under international humanitarian law to ensure the protection of civilians at all times," he told reporters.

A Palestinian rocket fired from the Gaza Strip struck a house in southern Israel today, causing damage but no injuries. NBCNews.com's Dara Brown reports.